<template lang="html">
    <scroll class="listview" :data="data" ref="listview">
        <ul>
            <li v-for="group in data" class="list-group" ref="listGroup">
                <h2 class="list-group-title">{{group.title}}</h2>
                <ul>
                    <li v-for="item in group.items" class="list-group-item" @click="selectItem(item)">
                        <img class="avatar" v-lazy="item.avatar" alt="" />
                        <span class="name">{{item.name}}</span>
                    </li>
                </ul>
            </li>
        </ul>
        <div class="list-shortcut" @touchstart="onShortcutTouchStart" @touchmove.stop.prevent="onShortcutTouchMove">
            <ul>
                <li v-for="(item,index) in shortCutList" class="item" :data-index="index">
                    {{item}}
                </li>
            </ul>
        </div>
    </scroll>
</template>

<script>
import Scroll from 'base/Scroll/scroll'
import {getData} from 'common/js/dom'
const ANCHOR_HEIGHT = 18;
export default {
    created(){
        this.touch = {}
    },
    props: {
        data: {
            type: Array,
            default: []
        }
    },
    computed: {
        shortCutList(){
            return this.data.map((group) => {
                return group.title.substr(0,1);
            })
        }
    },
    methods: {
        onShortcutTouchStart(e){
            let anchorIndex = getData(e.target, 'index');
            let firstTouch = e.touches[0];
            this.touch.y1 = firstTouch.pageY;
            this.touch.anchorIndex = anchorIndex;
            this.scrollTo(anchorIndex);
        },
        onShortcutTouchMove(e){
            let firstTouch = e.touches[0];
            this.touch.y2 = firstTouch.pageY;
            let delta = (this.touch.y2 - this.touch.y1) / ANCHOR_HEIGHT | 0;
            let anchorIndex = this.touch.anchorIndex + delta;
            this.scrollTo(anchorIndex);
        },
        scrollTo(index){
            this.$refs.listview.scrollToElement(this.$refs.listGroup[index], 0);
        },
        selectItem(item){
            this.$emit('select', item);
        }
    },
    components: {
        Scroll
    }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import "~common/stylus/variable"

.listview
  position: relative
  width: 100%
  height: 100%
  overflow: hidden
  background: $color-background
  .list-group
    padding-bottom: 30px
    .list-group-title
      height: 30px
      line-height: 30px
      padding-left: 20px
      font-size: $font-size-small
      color: $color-text-l
      background: $color-highlight-background
    .list-group-item
      display: flex
      align-items: center
      padding: 20px 0 0 30px
      .avatar
        width: 50px
        height: 50px
        border-radius: 50%
      .name
        margin-left: 20px
        color: $color-text-l
        font-size: $font-size-medium
  .list-shortcut
    position: absolute
    z-index: 30
    right: 0
    top: 50%
    transform: translateY(-50%)
    width: 20px
    padding: 20px 0
    border-radius: 10px
    text-align: center
    background: $color-background-d
    font-family: Helvetica
    .item
      padding: 3px
      line-height: 1
      color: $color-text-l
      font-size: $font-size-small
      &.current
        color: $color-theme
  .list-fixed
    position: absolute
    top: 0
    left: 0
    width: 100%
    .fixed-title
      height: 30px
      line-height: 30px
      padding-left: 20px
      font-size: $font-size-small
      color: $color-text-l
      background: $color-highlight-background
  .loading-container
    position: absolute
    width: 100%
    top: 50%
    transform: translateY(-50%)
</style>
